Growth of ‘black smoker’ bacteria at temperatures of at least 250 °C

Abstract

Complex communities of thermophilic bacteria have been cultured from the 350 °C waters emanating from sulphide chimneys, or ‘black smokers’, at 21 °N along the East Pacific Rise¹. Several of the bacterial communities were shown to grow rapidly at 100 °C and atmospheric pressure, producing methane, hydrogen gas and carbon monoxide. These gases are found in superheated vent water, having previously been attributed to abiogenic reactions. Before concluding that these ‘black smoker’ bacteria actually contribute to the chemistry of the superheated hydrothermal fluids, it was necessary to test their ability to grow and produce gases at in situ vent temperatures and pressures. Here we report that a bacterial community originally cultured from 306 °C water is capable of chemolithotrophic growth in a titanium growth chamber under in situ vent pressure of 265 atm and at temperatures of at least 250 °C. (At 265 atm, seawater remains liquid at temperatures of at least 460 °C².) Transmission electron microscopy of thin sections of bacteria cultured at 250 °C has revealed the presence of at least two morphologically distinct organisms.